a week ago we discovered a strange behaviour of our OSTicket v1.9.8.1installation.When our system got emails via imap login, tickets were created as expected and could be answered via email.However the tickets did not appear in the web interface and neither could be accessed with the ticket number received in the ticket creation notification.When we created a ticket from the web-interface there was no problem at all, the ticket appeared in the web interface as intended. We assume this behaviour started in early september, since there were no tickets created later who are accessible from the web interface. The error logs showed no unusual messages either. By brute forcing configuration changes we found a workaround: Uncheck "verify email address domain" in the email preferences of OSTicket and new tickets will appear in the web interface, when created via mail.

"It also sort of sounds like you have more than one version of osTicket installed and collecting emails. Which would also explain why you cannot see the tickets in the live one."

This is exactly what was the case. It is really embarrassing, but the problem did not have anything to do with OSTicket itself. When we moved to another server some time ago the OSTicket files remained on the old server. Although they were not accessible from the internet, there was a cronjob still running on the server which pulled the mails from the mailbox. We managed to shut it down so now hopefully this has an end.